The present invention relates to cylinder and/or valve deactivation in internal combustion engines.
Deactivation roller finger followers (DRFF""s) typically include a body and a hollow shaft upon which is disposed a roller. A locking pin assembly is switchable between a coupled and decoupled position wherein the shaft is respectively coupled to and decoupled from the DRFF body. A pin of the locking pin assembly is disposed within and carried by the hollow shaft. An output cam of an engine camshaft engages the roller.
With the locking pin in the coupled position, the shaft is coupled to the DRFF body. The shaft transfers rotation of the output cam engaging the roller to pivotal movement of the DRFF body, which, in turn, actuates an associated engine valve. With the locking pin assembly in the decoupled position, the shaft is decoupled from the DRFF body. Thus, rotation of the output cam is not transferred to pivotal movement of the DRFF body. Rather, rotation of the output cam is transferred via the roller to reciprocation of the shaft within grooves formed in the RF body. Therefore, the associated valve is deactivated, i.e., not lifted or reciprocated. Lost motion springs absorb the reciprocation of the roller and maintain the roller in contact with the output cam when the DRFF is in the decoupled mode of operation.
The position of the DRFF body relative to the output cam is established, in part, by one or more surfaces on the DRFF body that engage null lobes of the camshaft, and is important to the proper and reliable switching of the locking pin assembly. Wear caused by friction between the null lobes and the surface of the DRFF body engaged thereby may result in a shift in the position of the DRFF body in a direction toward the camshaft and/or output cam. A shift in the position of the DRFF body in a direction toward, or away from, the output cam may adversely affect the operation of the locking pin assembly by, for example, making the exact timing of the mode switching event somewhat unpredictable.
Therefore, what is needed in the art is an apparatus that reduces the wear of the null lobes and/or the surface of the DRFF body engaged thereby.
Furthermore, what is needed in the art is an apparatus that reduces friction at the interfaces between the null lobes and the surface of the DRFF body engaged thereby.
Still further, what is needed in the art is an apparatus that reduces or substantially eliminates any shift in the position of the DRFF body relative to the camshaft, and thereby improves the reliability and predictability of the mode switching of the DRFF.
The present invention provides a valve deactivation system for use with internal combustion engines.
The invention comprises, in one form thereof, an elongate camshaft having at least one lift lobe. The lift lobe has a lift portion and a base circle portion, and is affixed to or integral with the camshaft. A first null lobe is disposed on a first side of the lift lobe, and is affixed to or integral with the camshaft. A second null lobe is disposed on a second side of the lift lobe, and is affixed to or integral with the camshaft. A first journal bearing is disposed on the first null lobe, and a second journal bearing is disposed on the second null lobe. The journal bearings are configured for engaging a body of a deactivation roller finger follower to thereby reduce friction and wear of the roller finger follower body.
An advantage of the present invention is that it reduces friction between the null lobes and the surface of the DRFF engaged thereby, which, in turn, significantly reduces wear of those surfaces.
A further advantage of the present invention is that shifting of the position of the DRFF body relative to the camshaft is reduced.
A still further advantage of the present invention is that it is more economical than using special materials and/or coatings for the interfacial surfaces.